clump vs forgather

clump is a noun but forgather is not a noun.

Word	Noun	Adjective	Verb	Adverb
clump	Yes	No	Yes	No
forgather	No	No	Yes	No

As verbs, forgather is a hypernym of clump; that is, forgather is a word with a broader meaning than clump:

Other hypernyms of clump include assemble, foregather, gather, meet.

clump (noun)	forgather (noun)
a heavy dull sound (as made by impact of heavy objects)
a grouping of a number of similar things
a compact mass

clump (verb)	forgather (verb)
gather or cause to gather into a cluster	collect in one place
walk clumsily
come together as in a cluster or flock
make or move along with a sound as of a horse's hooves striking the ground